Document and Entity Information	6 Months Ended
	Sep. 30, 2011	Oct. 31, 2011
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2011
Document Fiscal Year Focus	2011
Document Fiscal Period Focus	Q2
Trading Symbol	ABMD
Entity Registrant Name	ABIOMED INC
Entity Central Index Key	0000815094
Current Fiscal Year End Date	--03-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		38,566,362